1. Field of the Invention
The invention relates to an extendible exhaust nozzle bell for a rocket engine of an aircraft or spacecraft. In particular, an extendible exhaust nozzle bell for a rocket engine of an aircraft or spacecraft which comprises a first part featuring a quasi-conical shape with smaller diameter fixedly arranged on a motor of a rocket engine and a second part featuring a quasi-conical shape with greater diameter arranged in a flexible manner with respect to this first part.
2. Discussion of Background Information
An extendible exhaust nozzle bell for a rocket engine of an aircraft or spacecraft is known from EP 0 516 519 B1 which comprises a first part of a quasi-conical shape with smaller diameter fixedly arranged on the motor of the rocket engine and a second part of a quasi-conical shape with greater diameter arranged in a flexible manner with respect to this first part. In a front stowed position relative to the flight direction the second part of the exhaust nozzle bell is arranged surrounding the first part located nearer to the rocket motor, and in a rear operating position relative to the direction of flight continuing the shape of the second part it is arranged further away from the rocket motor. To extend the second part of the exhaust nozzle bell from the stowed position into the operating position, an extension mechanism is provided that comprises several swiveling extension arms distributed over the circumference of the exhaust nozzle bell, which extension arms are coupled between the first part and the second part of the exhaust nozzle bell and connected in a hinged manner at a first end to a support structure provided on the outside of the first part of the exhaust nozzle bell. With the known exhaust nozzle bell, the extension arms are supported in a swiveling manner around an axis of rotation provided in the circumferential direction of the exhaust nozzle bell on the support structure attached to the first part of the exhaust nozzle bell in a radial plane containing the longitudinal axis of the rocket engine, and coupled in a pivoted manner on their second end to a tie rod that in turn is coupled in a pivoted manner with the other end to a point of application of force provided in the region of the front end of the second part of the exhaust nozzle bell on its outside. In the radial plane containing the longitudinal axis of the rocket engine the extension arms have a shape curved in an arched manner towards the front end of the second part of the exhaust nozzle bell, which shape during the extension of the second part of the exhaust nozzle bell permits a swiveling movement over a certain angle area encompassing the front end of the same.
Extendible exhaust nozzle bells for a rocket engine of an aircraft or spacecraft are known from U.S. Pat. No. 4,313,567 and U.S. Pat. No. 4,383,407, which in a similar manner comprise a fixedly arranged first part of a quasi-conical shape with smaller diameter and a second part of a quasi-conical shape with greater diameter arranged with in a flexible manner respect to this first part. To extend the second part of the exhaust nozzle bell from a front stowed position relative to the flight direction into a rear operating position relative to the flight direction, an extension mechanism is provided that comprises several transport screws arranged distributed over the circumference of the exhaust nozzle bell and coupled between the first and the second part of the exhaust nozzle bell. These transport screws are arranged parallel to the longitudinal axis of the rocket engine and can be driven via a rotary drive so that during their rotation the second part of the exhaust nozzle bell is extended towards the rear parallel to the longitudinal axis of the rocket engine.